1. Field of the Invention
The present invention relates to a system and method for guiding agricultural vehicles during planting, cultivating, spraying, harvesting or other operations.
2. Discussion of the Related Art
In modern farming operations, increased efficiencies and yields can be achieved by precision guidance of agricultural vehicles (e.g., tillers, seeders, sprayers and harvesters) over land areas to be cultivated. These precisely guided vehicles allow rows to be tilled in a relatively efficient manner.
The task of precision guidance of an agricultural vehicle involves defining a pattern to be followed by the vehicle, locating and orienting the pattern with respect to the area to be covered, and specifying various physical characteristics of the vehicle and implement, e.g., the width of the implement and the location of the implement with respect to the vehicle. With this information it is possible to define a series of paths for the vehicle to travel in an attempt to cover all cultivatable portions of the area. It is important to farmers to completely cover the area for a variety of reasons. One reason is that in tilling and planting operations, it is important to till and plant the entire area to maximize crop production, but to avoid tilling areas more than once to reduce costs, such as fuel costs, operator and equipment hours, etc. Another reason that is that in using insecticide, herbicide, fertilizer, and other spraying operations, if portions of the area are not covered, it is likely that no produce will grow. Likewise, if an area is covered more than once due to an overlap of paths, too much spray may be laid down on that portion of the area, so that emerging plants are harmed.
While calculating the series of paths needed to cover an area with substantially no gaps or overlaps is relatively straightforward when straight paths and/or concentric circular paths can be used, it is believed that this has not been achieved where the necessary or desirable paths have a curvature that varies along at least some of their length. In practice many fields have irregular shapes and contain obstacles (e.g., rocks and trees), so that geometrically predefined paths cannot readily cover them, and paths whose curvature varies along at least part of their length would be preferable.
Recently, the global positioning satellite (GPS) system and other similar systems (e.g. pseudolites or the GLONASS system) have been used to determine the geographic location of an agricultural vehicle to aid in guidance of the vehicle for efficient processing of an area to grow crops. One type of such a GPS system, referred to as Real Time Kinematics (“RTK”), is a process where GPS signal corrections are transmitted in real time from a reference receiver at a known location to one or more remote moving receivers, e.g. receivers mounted on a vehicle. By using differential corrections, the RTK system provides the most precise GPS positioning and is capable of compensating for atmospheric delay, orbital errors and other variables in GPS geometry. The result is positioning accuracy up to within a centimeter.
The application of GPS technology to farming is disclosed in U.S. Pat. No. 5,987,383 of Keller et al. (the “'383 patent”). According to the '383 patent, a vehicle makes a first pass or form line by causing a GPS equipped vehicle to travel between two locations in the area, e.g. along one edge. A second adjacent form line is calculated as a parallel swathing offset from the first line, where the swathing offset is the width of a spray pattern laid down by the vehicle or the area tilled in one pass. Guidance of the vehicle is aided by a display of a moving map and a light bar. The patent, however, does not disclose the details of the calculation of the swathing offset, and indicates that sub-meter accuracy is sufficient for most applications. U.S. Pat. No. 6,501,422 of Nichols shows a measurement device integrated with the GPS system to obtain three dimensional position data, as well as roll and pitch angles, and heading.
A prior system called AutoSteer, sold by the AutoFarm division of Novariant, Inc. (formerly known as IntegriNautics Corporation) of Menlo Park, Calif., the assignee of the present invention, uses RTK GPS to provide precision path guidance to farming vehicles carrying out farming operations. This prior product includes a display that shows the farmer a pattern of paths consisting of a series of parallel straight lines, even for concentric circles. The display shows the next proposed path as represented by a solid line in the series of paths, where the other paths are represented by dashed lines. The user can select a different path by steering towards one of the paths represented by dashed lines, in which case that path will become the proposed path and be displayed as a solid line.
It would be desirable if a system and method could be provided that is capable of guiding farm vehicles with high precision along arbitrary paths having varying curvature along at least part of their length, such that an area to be cultivated is substantially covered without skipping or overlapping portions thereof. It would further be desirable if the vehicle could be steered automatically, if alternative paths could be presented to and selected by the user through an interface that does not involve steering the vehicle, and if the selected sequence of paths could be recorded to form a template for later use on the same field.